A lot will depend on your room size and listening preferences, but the 20.1 was/is an excellent speaker, although I do agree it seems to need some power. But you can drive it quite successfully with less than 300 watts. Jim Winey used to make a point of telling me every time he saw me that the MG-20s he heard at Johnathon Valin's house sounded the best he had ever heard, driven by our MA-2s. I've also heard the MG20.7s driven by a pair of ARC Ref 150s which worked great as well.
Whatever sensitivity/efficiency number the speaker has, add 6db to deal with the fact that its a line source and you will get a better idea of how easy it is to drive.
Whatever sensitivity/efficiency number the speaker has, add 6db to deal with the fact that its a line source and you will get a better idea of how easy it is to drive.